From: Karel Gardas <kgardas@objectsecurity.com>
To: Giovanni Bajo <giovannibajo@libero.it>,
Steven Bosscher <stevenb@suse.de>,
Paolo Bonzini <bonzini@gnu.org>
Cc: GCC Mailing List <gcc@gcc.gnu.org>
Subject: Re: Compilation performance comparison of gcc3.4.1 and gcc3.5.0 2004-08-30 on MICO sources
Date: Thu, 02 Sep 2004 09:41:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.43.0409021105450.1006-100000@thinkpad.gardas.net> (raw)
In-Reply-To: <042301c49015$66c3fdd0$bf4e2597@bagio>
Giovanni,
I'm working on submiting bugreports right now, but I have observed one to
me very interesting fact. When I compile files preprocessed by 3.5.0 with
gcc3.4.1 I got slower compile-times, which means regression(s) are not
that dramatic. For example for typecode.cc I got from 40% to 30%. Also for
basic_seq.cc which should regress on all optimization levels, I now got
_no_ regression at all! In fact I got speedups! Look at following table:
Not preprocessed file:
File 341-O0 350-O0 Delta% 341-O1 350-O1 Delta% 341-O2 350-O2 Delta%
basic_seq.cc 3.77 4.21 -10.45 3.98 4.99 -20.24 3.82 5.72 -33.22
File preprocessed by GCC 3.4.1:
File 341-O0 350-O0 Delta% 341-O1 350-O1 Delta% 341-O2 350-O2 Delta%
basic_seq.cc 3.69 3.31 11.48 3.91 3.47 12.68 3.78 3.65 3.56
File preprocessed by GCC 3.5.0:
File 341-O0 350-O0 Delta% 341-O1 350-O1 Delta% 341-O2 350-O2 Delta%
basic_seq.cc 4.61 4.15 11.08 5.28 4.83 9.32 5.62 5.57 0.9
So it seems 3.5.0 is _always_ faster on preprocessed file than 3.4.1! So
either 3.5.0's libstdc++ library is bigger or 3.5.0's cpp is slower.
Size comparison of these two files look:
$ ls -la basic_seq.*.ii
-rw-rw-r-- 1 karel karel 1223628 Sep 2 11:13 basic_seq.341.ii
-rw-rw-r-- 1 karel karel 1243090 Sep 2 11:01 basic_seq.350.ii
I hope you understand that I'm reluctant to submit a regression bugreport
in this case. :-) I have also noted this thing in PR c++/17278 -- which is
for typecode regression...
When I compare table (1) 341-O0 - table (2) 341-O0 == 3.77 - 3.69 == 0.08
seconds spent for 3.4.1's cpp
The same for 3.5.0 is table (1) 350-00 - table (3) 350-O0 == 4.21 - 4.15 == 0.06
seconds, so even 3.5.0's cpp should be a bit faster. So it seems the
culprit should be libstdc++ in 3.5.0, but is it possible that the size
difference of 20kB i.e. 1% difference might do such big difference in
compilation speed?
Thanks,
Karel
On Wed, 1 Sep 2004, Giovanni Bajo wrote:
> Karel Gardas wrote:
>
> > 1) typecode.cc: 40% regression on O1 while 7% speedup on O2
>
> Can you please file a new bugreport with this -O1 regression, attacching this
> preprocessed testcase and the time reports to it? Also link Steven's message in
> it: http://gcc.gnu.org/ml/gcc/2004-08/msg01602.html, which contains the
> analysys of this.
> Then we can set that the new bug blocks PR 13776.
>
> I think it is better to track these issues with different PRs, and just
> connects them to PR 13776 (which is quite confusing at this point) just with
> the Bugzilla relationships.
>
> > -O2: 33% basic_seq.cc and following with 27% static.cc
>
> Can you open also a new bugreport about the regression of basic_seq.cc, which
> regresses at all optimization levels? Again, attacch preprocessed testcases, a
> comparison with 3.4 for all optimization levels, and the relative time reports.
>
> Actually, I should also note that at this point we cannot probably do much
> about compile time regressions at -O1/2/3. GCC 3.5 features more than 60 new
> optimization passes, so it is already a half miracle we don't regress
> everywhere. Code generation is also improved of course, so we have to lose a
> little somwhere. Of course, big regressions (>20% on files of non-trivial size)
> could probably still analyzed a little to see if we find obvious offenders.
>
> Thank you for doing this, it is of great help!
>
> Giovanni Bajo
>
>
>
--
Karel Gardas kgardas@objectsecurity.com
ObjectSecurity Ltd. http://www.objectsecurity.com
next prev parent reply other threads:[~2004-09-02 9:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-31 9:58 Karel Gardas
2004-08-31 10:12 ` Steven Bosscher
2004-08-31 10:28 ` Karel Gardas
2004-08-31 10:44 ` Paolo Bonzini
2004-08-31 10:46 ` Karel Gardas
2004-08-31 10:49 ` Steven Bosscher
2004-08-31 11:00 ` Paolo Bonzini
2004-08-31 11:24 ` Steven Bosscher
2004-08-31 19:30 ` Mike Stump
2004-08-31 12:48 ` Karel Gardas
2004-09-01 7:18 ` Paolo Bonzini
2004-08-31 10:55 ` Steven Bosscher
2004-08-31 13:57 ` Karel Gardas
2004-09-01 11:18 ` Giovanni Bajo
2004-09-02 9:41 ` Karel Gardas [this message]
2004-09-02 20:32 ` Compilation performance comparison of gcc3.4.1 and gcc3.5.02004-08-30 " Giovanni Bajo
2004-09-04 7:35 ` Karel Gardas
2004-09-02 9:44 ` Compilation performance comparison of gcc3.4.1 and gcc3.5.0 2004-08-30 " Karel Gardas
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